Now that macOS 10.13 High Sierra is out, it’s time to start taking about High Sierra stuff!
Munki 3 added support for upgrading macOS via the Install macOS.app for Sierra and High Sierra. A Munki admin need only download the installer from the App Store, and do
munkiimport /Applications/Install\ macOS\ High\ Sierra.app
to import the High Sierra installer into their Munki repo.
But there’s a wrinkle. Many people (including yours truly) were sometimes getting an installer application “stub” when downloading the Install macOS High Sierra application from the App Store. This “stub” application did not include the Contents/SharedSupport folder or its (very important) contents. The needed resources were instead downloaded “on-the-fly” when you ran the Install macOS High Sierra application.
This “stub” application is not useful as something to import into your Munki repo, or to use with AutoDMG or autonbi, or similar things. For these you really want the full installer, that is, one that contains all the needed installation resources in Contents/SharedSupport.
Many theories and ideas were put forth as to what caused one to get the stub vs the full installer. While I’m still not 100% sure about this, I think we’ve narrowed in on the cause.
It appears that when the App Store is downloading the installer app, it also uses softwareupdate to get the resources that normally reside in Contents/SharedSupport. If com.apple.SoftwareUpdate has been configured to use a CatalogURL that points to a softwareupdate catalog that does not contain product URLs for the needed Install macOS High Sierra resources, you get the “stub” application instead.
If, however, softwareupdate is using either Apple’s default CatalogURL, or is pointed to an internal CatalogURL that contains the needed products, you get the full installer.
Currently, the needed resources are Product 091-34298, “Install macOS High Sierra”, but this will almost certainly change over time.
TL;DR: to get a full High Sierra installer from the App Store, make sure softwareupdate is pointed at Apple’s softwareupdate servers or an internal server in which you have synced and made available the “Install macOS High Sierra” product.
Thanks to many people on the MacAdmins Slack for chipping in with their observations.